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Xenserver - Windows 2008 - Only see 4 processors

Posted on 2009-04-14
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Last Modified: 2013-11-11
Gents

Running xenserver 5 update 3 on a test Dell Poweredge 2950 with 2 quad core processors, I am only able to see up to a maximum of four processors within either windows 2003 server or windows 2008 server standard.

I understand proc limitations on standard are per socket thus should be able to see 8

I can confirm that looking at memeory and vcpu settings I have assigedn 8 vcpus for both machines in question.

What am I missing here ?

Chose xen over esxi becuase it allows up to maximum of 8 vcpus, but now am back at square one.

Greatly appreciate any advice
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Question by:malboteju
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by:kumarnirmal
ID: 24141644
Which Windows Server version will your guest run - 32 Bit or 64-Bit ?
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Author Comment

by:malboteju
ID: 24147266
thanks for your reply.

have tried both windows 2008 64 bit and 2003 32 bit, no change.

I read somewhere that windows sees xenserver processors as physical processors althought they are only cores. I have a total of 8 cores across two sockets (dual quad cores)

surely there must be sa fix for this by xen/citrix, I wonder if this is the same with vmware
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Expert Comment

by:sholford
ID: 24234534
The problem is that XenServer virtualises each core as a separate physical processor in its own socket. Windows Server 2008 and 2003 are limited to 4 sockets, so you can only see 4 of your 8 cores in the task manager.

If you look in the Device Manger you'll see all 8 cores because Windows sees them all, but won't let you use them.

If you look in the XenServer Host console in the Hardware section, it will report 8 physical CPUs too.

The following solution has been claimed to work and I suggest you try it, but I haven't personally managed to get it to work.

In XenCenter set the VCPUs for your VM to 2.

Then enter the attached code snipped into the XenServer Host console. To find the UUID for your VM, type xe vm-list (select it, right click and copy then paste when you need to enter the UUID as it's quite long).

Now boot the VM and the task manager should show all 8 cores.



xe vm-param-set platform:cores-per-socket=4 uuid=xxxxxx
 
xe vm-param-set VCPUs-at-startup=8 uuid=xxxxxx
 
xe vm-param-set VCPUs-max=8 uuid=xxxxxxx

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Author Comment

by:malboteju
ID: 24274329
thanks that didnt work for me either...

I tried win2k3 vm on the same box same result

even tried setting cores-per-socket=2 instead but no effect
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Expert Comment

by:sholford
ID: 24274779
This seems to be software problem that has only recently been discovered and is starting to be discussed.

http://forums.citrix.com/thread.jspa?messageID=1376811

Hopefully there will be a fix in the next update of XenServer.
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Accepted Solution

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malboteju earned 0 total points
ID: 25839851
switched to vmaware !
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Expert Comment

by:CampusHosting
ID: 34062346
Follow up comment, I ran up against the same problem and the solution from "sholford" worked great.  One note, I'm running XCP 0.5.0, two seperate machines.  The first is a slightly older Dell PE2950 with dual quad core Xeon E5410's (quad core but no hyperthreading).  The other is much newer with dual Xeon E5630's (quad core *and* HT).  On the first box I set cores-per-socket to 4, Vcpus Max and Startup to 8.  My Windows Server 2008 R2 Standard guest shows 2 cpu's in system properties, and Task Manager shows 8 as expected.

On the other system I set cores-per-socket to 8 to account for 4 cores and 2 HT threads per core, then Vcpus Max and Startup to 16.  That Windows Server 2008 guest also shows 2 cpu's in system properties, and 16 in Task Manager.

The real test came with SQL 2008 x64 Standard, which will use a maximum of 4 cpu's.  Previously on my PE2950 host the OS saw all 8 Vcpu's, but SQL Standard edition would only utilize 4 of them due to licensing contraints.  Now when I run a data scramble test against a DB for our product it fully utilizes all 8 Vcpu's because it see's the system as having only 2 sockets/cpus.

This was a particularly important issue for us because we license from Microsoft on a per-socket monthly fee, and SQL Server 2008 Enterprise is significantly more expensive than Standard, but Standard suits our needs just fine otherwise.
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Expert Comment

by:dynasis
ID: 34666902
I tried it on 2 differant XenServer v5.6 and it didn't work on either of them.
We are running Windows 2008 R2 Standard in the VM
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Expert Comment

by:MMHDU
ID: 35996749
The suggested solution works great except you need to set the max vcpu's before you set the startup vcpu's.

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